I have just recently been working on implementing Torque (paid version) on my Android Xoom tablet.

Both options take some time to set up, but seem comparable, dashboard display wise.

It depends what you plan to do with your car setup, tablets are less expensive to implement, but at the moment seem to have some limitations, a lot of the apps require an internet connection, where as the PC route came from old school and has a lot of history in not having an internet connection, this is changing, we will all probably need tethering to our phones or a dedicated hotspot to be feature complete whichever route you go.

TruckPC - gutted, being used for test setup
BoatPC - All in 1 in cuddy, N7 using VNC on dash, RR
BlazerPC - Nexus 7 with Timur's USBROM